Welded joint

ABSTRACT

DISCLOSED IS A SUPPORT OR SUSPENSION FOR AN ANODE IN AN ALUMINUM ELECTROLYTIC CELL, INCLUDING A STEEL MOUNTING PLATE AND A CONTACT ROD OF ALUMINUM OR COPPER WELDED AT ONE END PORTION THEREOF TO AN END PORTION OF THE PLATE SO THAT THE AXIS OF THE ROD IS IN THE PLANE OF THE PLATE. THE END PORTION OF THE ROD IS PROVIDED WITH A DIAMETRAL SLOT DIRECTED TRANSVERSELY TO THE PLANE OF THE PLATE AND THE WELD IS INTERRUPTED BY THE SLOT.

July 25, 1972 K. SPRINGER 3,679,569

WELDED JOINT Filed Oct. 15. 1970 5 sheets-sheet 1 Fig. 7

July 25, 1912 Filed Oct. 15. 1970 Fig. 2

- K. SPRINGER WELDED JOINT 3 Sheets-Sheet 2 a II/II July 25,1972 K. SPRINGERY WELDED JOINT 3 Sheets-Sheet 5 Filed Oct. 15. 1970 Fig.3

United States Patent 3,679,569 WELDED JOINT Kurt Springer, Rheiufelden, Germany, assignor to Swiss Aluminum Ltd., Chippis, Switzerland Filed Oct. 15, 1970, Ser. No. 81,056 Claims priority, application Switzerland, Oct. 24, 1969, 15,879/69 Int. Cl. B01k 3/04; C22d 3/12 US. Cl. 204-286 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION During the production of aluminum by the fusion electrolysis of an aluminum oxide solution in a cryolite electrolyte, pre-baked carbon or graphite anodes are now more frequently chosen to serve as the anodic current supply. As a rule, a current conductor, consisting of bundled copper or aluminum-rods or of a single cast aluminum bar, is located above the electrolytic cell. The pre-baked anodes and the current conductor are connected by means of copper or aluminum contact rods, which are clamped onto the current conductor. It is known to use a perpendicular mounting plate to connect the contact rod with the pre-baked anodes. When this is done the mounting plate is rammed or pressed into the anode or is cast in by means of a liquid carbonaceous mass or liquid cast iron, and may be screwed together with the contact rod or be welded to same. The plate must, however, be made of steel because of the high temperatures in the vicinity of the bath.

The screw-type connection between the contact rod and the anode' mounting plate has the disadvantage that due to heat and gasaction the contact resistance increases with time and, accordingly, the current carrying capacity deteriorates. A welded connection or seam which is attained by ensuring that a lower section of the contact rod is welded to a vertical cut-out section in the mounting plate is superior to the screw connection as far as electrical conductivity is concerned. Even in this case, however, certain disadvantages arise which are brought about by the different coeflicients of thermal expansion of the steel, copper or aluminum, thereby causing cracks to frequently occur in the welded seam, which likewise have an adverse eifect on the current carrying capacity. As a rule, the contact rods have a rectangular or quadratic cross-section and are rolled, extruded or continuously cast. In the case of the anodes, which for example carry 4,000 to 6,000 amps, the cross-section of the copper rods may be approximately 80 x 25 mm. In the case of aluminum rods, it can either amount to 80 x 80 mm. or to 185 x 90 mm. Depending on the cell construction, the length of said rods can vary between 1.8 and 3 m.

The mounting plates, for example, can be 50 mm. thick, 800 mm. long and 500 mm. high, such as in an anode with a cross-section of an approximate length of 1,100 mm. and an approximate width of 500 mm. The outer contour line of the mounting plate in a preferred embodiment has an approximately rectangular shape.

3,679,569 Patented July 25, 1972 2 SUMMARY OF THE INVENTION One of the principal objects of the present invention is to avoid the drawbacks of the prior art with respect to a welded joint between an aluminum or copper contact rod and a steel mounting plate.

It is another object of the present invention to provide for a welded joint which is simple to accomplish.

It is yet another object of the present invention to provide for a welded joint that is adapted to fit into existing machinery used in aluminum fusion electrolytic cells.

According to the invention the foregoing objects are essentially accomplished by providing an anode support comprising a steel carrier plate and a contact rod of aluminum or copper with its axis in the plane of the plate, the end of the rod has a diametral slot across it, perpendicular to the plane of the plate, and the plate and rod are welded together on both sides of the slot, the weld being interrupted by the width of the slot. By the eifect of this slot, the stresses due to welding and heat can equalize during the welding and afterwards, so that no cracks occur in the weld and a satisfactory flow of current through the weld is ensured. The slot can be made in a variety of shapes, for example with parallel walls, or tapered and widening downwards or widening outwards. Preferably the walls are parallel. The width is not critical and can for example lie between 1 mm. and 10 mm. A width of 2 mm. has been found satisfactory. Preferably the weld is made on both faces of the carrier plate. of course it is preferable for the plane of the plate to lie centrally in the cross-section of the contact rod. The contact rod extends into a cut-out in the plate which may be mm. to 200 mm. deep, and preferably the dimension of the slot along the axis of the rod is substantially equal to the depth of the cut-out.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawings, in which:

FIG. 1 is a schematic side view, partly in section, with an aluminum fusion electrolytic cell;

FIG. 2 is a front view of a lower section of a contact rod portion of an electrolytic cell showing a welded joint of the instant invention; and

FIG. 3 is a side view in detail, similar to FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT An electrolytical cell 10 has a tank 11 which like the remaining components of the electrolytic cell need not be shown in detail, since such cells are well known to the expert in the field. The tank 11 contains a molten cryolite electrolyte 12 which contains aluminum oxide in dissolved form. The cryolite electrolyte is covered by a layer of slag 13, above which there is a layer of aluminum oxide 14. During the electrolytic process the separated liquid aluminum 15 accumulates at the bottom of the cell 10. The electrolytic current is supplied on the cathode side by bars 16 (of which only one is shown in FIG. 1).

An anodic current conductor is mounted above the electrolytic cell 10 and carrying the current by contact rods 18 and mounting plates 19 to pre-baked carbon anodes 20 which are immersed in the cryolite electrolyte 12. With the aid of a rod-locking device 21 the contact rods 18 are clamped to the current conductor 17. The contact bars 18 at their lower sections are welded to the mounting plate 19. The weld beads are designated at 22 wherein tension or stress cracks frequently occur.

FIGS. 2 and 3 show the manner in which the welded joint between the contact rod 18 and the mounting plate 19 is fashioned in accordance with the present invention, so that tension or stress cracks will neither form during nor after the welding procedures.

The welded joint formed in accordance with the present invention is characterized by the fact that at the lower section of the contact-rod there is formed a slit 23 which extends upward vertically in thecenter of the contact rod 18 and is positioned perpendicular to the mounting plate 19. In so doing the welded seam 22 is interrupted along the width 24 ofthe slit 23. In order to accommodate entry of the lower section of the contact rod 18, a cut-out sec: tion 25 is provided in the mounting plate 19. At the lower section of contact rod 18, the slit 23 is suitably milled, or worked in:- another manner, this being done to such a degree that the vertical length of the slit 23 approximately corresponds to the depth of the cut-out section 25 of the mounting plate 19. I p The mounting plate 19 may have sloping sides 26 at its upperedge, but it is not absolutely necessary. On the other hand, a recessed area 27 at the lower section of the mounting plate 19 may be omitted.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art. I Having thus described the invention, what I' claim as new and desire to be secured by Letters Patent is as follows:

1. In an aluminum electrolytic cell, an anode support comprising a steel mounting plate and a contact rod of aluminum or copper with its axis in the plane of the plate in which the end of the rod has a diametral slot across it, perpendicular to the plane of the plate, and the plate. and rod arewelded together on both side of the slot, the weld being interruptedby the width of the slot.

} -2.--An anode' support according to claim 1 in which the welded end of the rod lies in a cut-out in the plate, and the dimension of'the slot; along the axis of the rod is substantially equal to the depth of the cut-out.

v References Cited m UNITED STATES PATENTS JOHN H. MACK, Primary Examiner R. J. FAY, Assistant Examiner US. 01. X.R. 

